Valorization of contaminated Eichhornia crassipes in phytoremediation of tannery waters: Bioethanol production

• Reduction of macrophytes, Eichhornia crassipes , through a combined treatment (phytoremediation and bioethanol production). • Biomass optimization using a Box-Behnken experimental design to obtain sugars. • Accessible biomass to phytoremediate chromium present in tanning industries. In this research, a sustainable system to obtain bioethanol from Eichhornia crassipes biomass contaminated with total chromium was developed A phytoremediation system was applied in order to remove chromium from tannery wastewater, using the resulting biomass as raw material. The dry biomass (DS) was subjected to an optimized pretreatment using a Box–Behnken experimental design in which 45 treatments were evaluated. The structural changes in the biomass were characterized by SEM and FTIR. After this, hydrolysis with 3 % H 2 SO 4 using a steam explosion was performed. Chromium retention was higher in roots (99.29 %), leaves and stems (94.14 %). Treatment using C 0 = 1.56 % had the highest removal efficiency (R = 95.51 %), followed by 3.13 % (93.47 %). Regarding valorization, the bioethanol yield reached 71.35 % in relation to reducing sugars and 0.12 mL/g with respect to the initial biomass. These results confirm the feasibility of integrating phytoremediation with bioethanol production as a sustainable alternative for treating tannery effluents.